1. Field of the Invention
The present invention relates to a three-dimensional map display system that displays a three-dimensional map.
2. Description of the Related Art
An electronic map displayed on the screen of, for example, a navigation system or a computer may be a three-dimensional map that expresses features such as buildings three-dimensionally. The three-dimensional map is generally displayed by drawing three-dimensional models by, for example, perspective projection. In the three-dimensional map, the ground surfaces and water systems such as sea are expressed by three-dimensional polygons as described below.
Japanese Patent Laid-Open Application No. JP 2000-306073A discloses a technique of generating and displaying ground surface polygons and sea surface polygons from altitude data provided in meshes. Japanese Patent Laid-Open Application No. JP 2006-259035A discloses a technique of generating a ground surface polygon, painting parts other than the ground surface with the same background color as that of the ground surface, and displaying a water system polygon over the ground surface polygon, so as to make misalignment at the boundary between the ground surface and the water system less noticeable.